1. Field of the Invention
This invention is directed to stack capacitors for DRAM and FRAM and, more particularly, to a compound electrode stack capacitor, as well as simple processes for fabricating the new stack capacitor electrodes. The electrode structures are made from materials suitable for use with high-dielectric constant materials (e.g., Pt) and are compound because the component parts of the electrode structures are either deposited in separate steps or formed from more than one layer of material.
2. Description of the Prior Art
The incorporation of high dielectric constant materials into small geometry capacitors suitable for Gigabit scale DRAM introduces fabrication challenges relating to topography, electrode material patterning, reaction of high-epsilon materials with Si contact and ultimate density/scalability. Similar challenges pertain to the fabrication of ferroelectric memory cells for ferroelectric RAM (FRAM) and other nonvolatile RAM (NVRAM). Most fabrication schemes for making the electrodes for nonplanar memory cells (a category of devices including both capacitors or "dielectric memory cells" and ferroelectric memory cells) rely on either chemical-mechanical-polishing (CMP) and reactive-ion-etching (RIE). However, these processes to pattern electrode materials such as Pt and other noble metals are still under development; while some processes may eventually be useable in one form or another, there is no guarantee that completely suitable ones will be found.
Suitable electrode materials and fabrication/patterning processes must be developed if high-epsilon dielectric and ferroelectric materials are to be integrated into microelectronic devices. Noble metals and their alloys are often preferred as electrodes for these applications, in part because of their resistance to oxidation during dielectric deposition. However, these materials can be difficult to pattern.
It is an object of the present invention to provide an electrode structure that can be fabricated without CMP or RIE-patterning of a thick electrode layer.
It is another object of the present invention to provide a tall stack electrode having noble metal surfaces and a method of fabrication which does not require CMP or a thick noble metal etch.
It is yet another object of the present invention to provide a noble metal cup electrode whose method of fabrication does not require CMP or fill/etchback.